Process for the production of n-alpha-olefins by the am (alkyl metal) technique



Oct. 11, 1966 O J. SERRATORE ETAL 3,278,633 PROCESS FOR THE PRODUCTIONOF n-a-OLEFINS BY THE AM (ALKYL METAL) TECHNIQUE Filed May 15, 1963Joseph SerrcTore David A. Gudelis I Ronald Vcnder Llnden Inventors ByWhelun,Brenner,Choson,Murx 8Wnght United States Patent 3,278,633 PROCESSFOR THE PRODUCTION OF Il-oc-OLEFINS BY THE AM (ALKYL METAL) TECHNIQUEJoseph Serratore, David A. Gudelis, and Ronald Vander Linden, Sarnia,Ontario, Canada, assignors to Esso Research and Engineering Company, acorporation of Delaware Filed May 15, 1963, Ser. No. 280,590

, 5 Claims. (Cl. 260-68315) weight aluminum trialkyls corresponding tothe displacing olefins, and (3) separating the displaced highermolecular weight olefins .as product from the lower molecular weightaluminum alkyls formed in the displacement reaction, which lower alkylsare recycled to the process. Still more particularly, this inventionrelates to the use of two displacement reactions, first employing anolefin having at least 18 carbon atoms and upto about 22 carbon atomsand then employing ethylene or propylene in a manner which avoids orminimizes isomerization in the olefin product as well as loss of C or Calkyl alumihum reactant.

It is-to be noted that olefin employed in the first displacement zone ishereinafter referred to as a C -C displacing olefin for ease ofdescription. It is to be understood, however, that such olefin may alsobe one having a Poisson distribution about the desired number of caribonatoms, i.e. C -C Thus, the present invention contemplates 2. displacingolefin having a 0 Poisson distribution as well as a displacing olefinhaving a C Poisson distribution as here later set forth in greaterdetail.

Some prior art processes have been limited generally to the productionof C C olefins, since no practical methods were known for completelyseparating olefins boiling close to C -C olefins from the C or C alkylaluminum remaining after the displacement reaction. Thus the C andhigher olefins could not be economically distilled overhead from theliquid alkyl aluminum due to the relatively low decompositiontemperature of said alkyl aluminum and/or the closely similar boilingranges of the lower alkyl'aluminum and these higher olefins. Thus,according to the same prior art processes, it was considered necessaryto closely regulate the growth conditions so as to obtain a minimumamount of C and higher olefins. Additionally, those higher olefins whichwere formed required removal by purging, which involved the loss of animportant amount of commingled,

valuable alkyl aluminum compounds. Further, in order to keep these alkylaluminum purge losses to a minimum, the C and higher olefin content ofthe recycle aluminum alkyl stream was often built up to fairly highlevels,

which also deleteriously affected the process due to the cost ofcirculating large amounts of this material.

In order to produce the desired full range of straight chain olefins itwas proposed to employ two displacement reactions, the first employing aC -C olefin and the second employing ethylene. Such double displacementmethod was found to be highly practical in the separation of olefins inthe C -C g range from C -C alkyl aluminum resulting from the firstdisplacement reaction and an improvement over the existing state of theart.

3,278,633 Patented Oct. 11, 1966 However, since separation of thedisplaced olefinic product from the resulting C -C trialkyl aluminumrequired a fractionation step, certain inherent disadvantages were foundto be present in the double displacement reaction of the prior art. Forexample use of the fractionation step involved relatively long exposuretimes .at high reaction temperature and in costly fractionationequipment. Thu-s, because of the thermal sensitivity of the olefins andaluminum trialkyls to isomerization and addition reaction difficulty inobtaining high purity n-alpha-olefins was encountered. Further, in orderto accomplish the first displacement, large molar ratios of C -Cdisplacing olefin to aluminum alkyls were required, for example,hexene-l displacement required a 50 to 1 molar ratio in order to effectthe desired displacement.

In addition in order to design an economic commercial olefin plant ofthis type, it is necessary to have available triethyl aluminum or otherlow alkyl aluminum such as tripropyl aluminum for the growth reaction,at a reasonable cost. It is therefore considered essential that thetriethyl or tripropyl aluminum growth reactant be recovered inrelatively pure form for recycle to the growth reactor as alkyl growthreactant.

It is an object of this invention, therefore, to provide the art with anovel continuous process for producing olefins over the broad spectrumof C C which have little or no branchiness in the molecule due toisomerization. It is a further object of this invention to provide theart with a process for the manufacture of the aforesaid straight chainolefins having a favorable effect on the critical variables encounteredin the thermal displacement reaction, viz: reaction temperature,residence time, and the mole ratio of displacing alpha-olefin toaluminum alkyl. It is also an object of the present invention to providethe art with a simplified process whereby elaborate and costlyfractionation equipment may be eliminated entirely or substantiallyreduced. It is a further object of this invention to provide a processfor the preparation of straight chain olefins and concurrently therewitha maximum of triethyl or tripropyl aluminum recovery in a sufficientlypure state for recycle to the growth reactor. These objects and otherswhich will become apparent are eifected by resort to the followingdescribed process with specific reference to the appended drawing,schematically illustrating the process. In the exemplary processdescribed, triethyl aluminum is employed as growth reactant whereas thisinvention also envisions the use of tripropyl aluminum as growthreactant, in which case propylene will be employed in the seconddisplacement zone. In addition, the present invention also contemplatesalternate metals in place of the disclosed aluminum. Thus, other metalscan replace aluminum providing (1) the volatility of the proposed lowermetal alkyls is sufficiently low enough so that vaporization lossesduring displacement could be minimized, and (2) the lower metal alkylscan readily dissociate to the intermediate alkyl metal hydrides in amanner similar to aluminum alkyls. Representative of such metal alkylsare gallium alkyls, e.g. gallium triethyl, and beryllium alkyls, e.g.beryllium triethyl.

In accordance with the present invention a process for the preparationof olefins comprises reacting a trialkyl aluminum reactant having 2-3carbon atoms per alkyl group with ethylene under elevated temperaturesand ethylene pressures whereby a trialkyl aluminum growth product havingfrom about 2-24+ carbon atoms per alkyl group is obtained, reacting saidgrowth product in a first displacement stage with an olefin having atleast 18 carbon atoms and up to about 22 carbon atoms to obtain a firststage alkyl aluminum displacement product which is mixed with olefinscorresponding in chain length to the alkyl groups in said alkyl aluminumgrowth product, separating from said mixture olefins having avaporization point below said first stage alkyl aluminum displacementproduct, reacting in a second stage said first stage alkyl aluminumdisplacement product with a. C -C olefin to obtain a mixture of higherolefins and a second stage alkyl aluminum displacement product anddistilling overhead from said mixture said second stage alkyl aluminumdisplacement product from said higher olefins.

The basic growth reaction involved in the present proc- 'ess can betypified by the following equation:

wherein R, R and R" attached to the aluminum atom represent normal alkylradicals of the same or different molecular weight.

In the growth reaction, triethyl aluminum or tripropyl aluminum isreacted with ethylene at a temperature between 200500 F. and an ethylenepartial pressure of 350 to 7500 p.s.i.g. for 0.5 minute to an hour ormore. Ethylene radicals are thereby disposed in between the aluminum tocarbon bonds in the triethyl aluminum, enlarging the size of the alkylradicals on the initial trialkyl aluminum by carbon number multiples oftwo until a trialkyl aluminum product averaging C -C carbon atoms peralkyl is formed. Starting with triethyl aluminum the growth product willcontain even numbered alkyl groups whereas with tripropyl aluminum thegrowth product will 'contain odd numbered alkyl groups. With regard tothe growth product R, R and R" referred to above may in some instancesbe the same; for example, tributyl aluminum, trihexyl aluminum,tripentyl aluminum, trioctyl aluminum, trinonyl aluminum, triododecylaluminum, tri tetradecyl aluminum, trihexadecyl aluminum, trieicosylaluminum, tridocosyl aluminum, etc. However, in most instances the alkylgroups of the trialkyl aluminum growth product will be different. Asexamples, the growth product may contain a trialkyl aluminum compoundsuch as ethylhexyloctyl aluminum, dibutyloctyl aluminum,octyldodecylhexadecyl aluminum, as well as mixed odd numbered trialkylaluminum compounds when tripropyl aluminum is employed. Occasionally,alkyl aluminum hydrides occur during growth. Insofar as the growthproduct is concerned, the lowest boiling trialkyl aluminum is triethylaluminum which boils close to normal C alpha-olefin under pressuresnormally employed. Tripropyl aluminum boils close to the C olefin andtri butyl aluminum within the range of C C olefins.

In the drawing, growth reaction zone 1 may be any simple reactor capableof withstanding the necessary pressures and temperatures notedpreviously. Preferably, however, this reactor will comprise a tubularserpentine-like coil of from 50 to 300 feet in overall length. Since thegrowth reaction is exothermic and it is necessary to remove heat, heatexchange means must be employed in order to control temperature. Whilemany heat exchange techniques are available it is preferred to use atube within a tube. The internal tube of, for example, a diameter of/2"10, preferably under 6", comprises the reactor 'wherein triethyl isreacted with ethylene. The outer tube which completely encases the innertube but which otherwise is not connected thereto will contain thecirculating coolant. The outer tube should, of course, have an internaldiameter substantially greater than the outside wall of the internaltube to increase heat exchange efficiencies. Alternatively, the tubesmay be immersed in a cooling medium.

Ethylene, preferably in a relatively pure state, is introduced into thereaction zone via line 10 with makeup triethyl aluminum via line 12.Triethyl aluminum in line 11 is recycled from a later stage in theprocess and line 12 is provided to permit adding small amounts oftriethyl aluminum make-up. 'If desired there may be provided multipointinjection of the ethylene and/ or triethyl aluminum; however, this isnot considered necessary. After the growth reaction is completed withinthe specified time the growth reaction product containing some unreactedtriethyl aluminum and ethylene as Well as trialkyl aluminum containingalkyl groups of from 2 to about 26 carbon atoms is removed via line 13and passed through to displacement reactor 3 wherein the firstdisplacement is eifected. Preferably ethylene is flashed off prior tothe first displacement step by conventional means in flash chamber 2 andrecycled to the growth reaction stage via line 14 as ethylene feed.

Prior to the first displacement reactor 3, C -C displacing olefin isintroduced via line 15 into the growth reaction product stream 13. The C-C displacing olefin is employed in a mole ratio of from about 3:1 to30:1 mole of displacing olefin per mole of aluminum alkyl growth productand preferably from 5:1 to 7:1. The first displacement reaction indisplacement reactor 3 is carried out at a temperature in the order offrom 200 to 350 C., preferably 250- to 300 C., pressures of from 0.1 mm.to 2 atmospheres, preferably 5 to 20 mm. of Hg and for a residence timeof from 0.1 second to 2 hours preferably 1 to 40 seconds, therebygenerating olefins corresponding to the alkyl groups in the alkylaluminum growth product and C -C alkyl aluminum compounds.

As the displacing olefin for the first displacement there should beemployed any olefin having from at least 18 carbon atoms up to about 22carbon atoms. Thus, suitable displacing olefins include octadecene-l,nondecene-l, eicosene-l, heneicosene-l and docosene-l. As hereinbeforementioned, the present invention also envisions use of an olefin havinga Poisson distribution that is an olefin having, for example, from a CPoisson distribution to a C Poisson distribution. Thus, it is Within thescope of the present invention to employ the C olefins obtained by thedisplacement reaction practiced herein. In practice therefore, thedisplacing olefin resulting from a C average growth alkyl would be a Colefin product with a Poisson distribution in mole percent as follows.

Olefin Mole percent C 4.13 C 2.25 C 1.10 (3 1 08 In accordance with theinstant invention, displacement in displacement reactor 3 with C Calpha-olefins yields displaced products which are easily separated in asingle short residence time flash operation, thereby minimizingisomerization and side reaction. As heretofore noted in prior artdisplacement reaction, in order to maintain high conversion in thedisplacement reaction, a high molar ratio of C -C displacing olefins toaluminum trialkyls is required. However, with the use of O -C displacingolefins, lower molar ratios of olefin to aluminum trialkyls can beutilized to apparent great advantage. This is attributed to the factthat the displaced Cz-Ggo alpha olefins are continuously separated fromthe resulting aluminum trialkyl product and are continuously removedfrom the displacement reactor, via line 16, by means of a gas stream orby a reduction in operating pressure. Hence the displacement reactioncan approach a complete conversion since the C C displacing olefins aresubstantially all in the liquid phase while successful use of C Cdisplacing olefins depend on solubility.

Thus, the thermal displacement reaction of the instant invention employsa displacing n-alpha-olefin with a high boiling point in order that thedisplaced alpha-olefins can be vaporized and removed from the reactorwhile the high-boiling displacing n-alpha-olefin remains in the liquidphase in the reactor. Such practice permits the use of lower mole ratiosof displacing alpha olefin to growth aluminum trialkyl in comparison tothe C -C olefin displacement of the art, since the displaced olefin willvaporize andthe undistilled displacing alpha-olefin thereby increases inconcentration in the liquid phase, which adds rapidly to the aluminumdialkyl hydride intermediate initially formed in the liquid phase. Forexample, if docosene-l is employed in the displacing alphaolefin sinceits boiling point (224 C. at mm. Hg) is sufficiently high to allow it toremain in the liquid phase at the displacement temperature utilized(e.g. 310-315 C.), the following initial-sequence occurs:

(a) The spontaneous splitting of alpha-olefin from the aluminum trialkyl(b) The addition of docosene-l to the aluminum hydride bond The reactioncontinues until all three alkyl groups R are displaced by docosene-l. Assoon as the olefin is formed, it is vaporized and carried away thusshifting the reaction to the right and aiding the displacement reaction.

The displacement reactor 3 utilized in the instant invention can be atubular reactor, a mixed film evaporator or molecular still, a shortresidence time fractionator or any other reactor designed so thatvolatilized alpha-olefins can be removed rapidly, e.g. by using acarrier gas. Suitable for the reactor is a vacuum jacketed fractionationtower packed, if desired, with glass helices and equipped with areboiler and preheater. The foregoing examples are deemed illustrativeand not limiting on the scope of the instant invention. Optimizationexperiments can be run by one skilled in the art in order to determinethe equipment most adaptable to the invention under the particularcircumstances encountered.

Referring again to the example and the drawing, the docosene-l displacedstream will contain principally tridocosyl aluminum and C normalolefins. Preferably this tridocosyl aluminum containing stream is passedto a cooler which can be maintained at pressures of about 0.1 mm. orless to 10 atmospheres or more and temperatures of about 40 to 150 C.The tridocosyl aluminum-olefin containing stream is then passed via line17 onto the sec ond displacement reactor 4. The mixed tridocosylaluminum-olefin stream is passed through line 17 with fresh ethylenefrom line 18 into displacement reactor 4, as well as recycle ethylenefrom line 19. In displacement reactor 4 wherein ethylene will bedisplacing the docos'yl groups of the tridocosyl aluminum, slightlyhigher pressures may be employed, e.g. /2 to 20 atmospheres andessentially the same temperature and residence time may be utilized asin the prior displacement reaction. Thus, in a second stage displacementzone the alkyl groups of the first stage alkyl aluminum displacementproduct are displaced by an olefin having 2 or 3 carbon atoms, i.e.ethylene or propylene and preferably 2 carbon atoms, i.e. ethylene.There is then obtained a second stage alkyl aluminum displacementproduct which can be separated from the remaining olefins and recycledas described hereinafter. In this specific example the product from thesecond displacement reaction which is removed via line 20 will containethylene, docosene-l, triethyl aluminum and C olefins. The ethylene maybe flashed overhead via a conventional flash drum 5 and after separationethylene may be recycled via line 19 back to the second displacementreaction zone. The remaining triethyl aluminum and C olefin are passedvia line 21 to the triethyl aluminum fractionator or evaporator tower 6wherein triethyl aluminum is taken overhead via line 11 and recycled tothe growth reaction zone via line 11. Normal alpha olefins having littleor no branchiness are recovered via line 22. The temperatures withinfractionator tower 6 must be maintained sufficiently low to avoid a backdisplacement, i.e. displacement of the ethyl radicals in the triethylaluminum by the higher molecular Weight olefins, and also isomerizationof the alpha normal olefins. Preferably, the temperature within thesplitter tower should not exceed 225-275 F. Maximum pressures, ofcourse, should be adjusted to coincide with the maximum temperaturesdesired in the tower, e.g. 0.5 to 50 mm. Hg, preferably 1-10 mm. Hg.

In order to facilitate a clear understanding of the invention, theinitial displacement step of the process of this invention isillustrated by the following preferred embodiments described in detail.

EXAMPLE I In this example, as well as in the following Examples 11 to Va growth alkyl of a C average chain length was utilized. A comparativecomposition analysis of the growth alkyl was determined and issummarized in the following Table I.

Table 1 Components, weight percent Analysis 1 Ethane n-Butane 3. 00n-l-Iexane 6. 09 Hexene-l. 0. 22 Unknown 0. 05 n-Octane 9. 40 10. G8Ootene-l 0. 24 0. 71 Unknown.. 0. 04. n-Decane 12. 41 12. 8 Decene-L 0.75 0. 78 Unknown 0. 1O n-Dodecane. 14. 25 13. 93 Dodeeene-l 2. 24 1. 57Unknown 0. 14

Doeosene-l 0. 14 0. 43 n-Tetraeosane. 1 09 1. 21 Tetracosene-l. 0. 21n-Hexac0sane 0. 71

1 Sample hydrolyzed in cold methanol and analyzed by gas ehromatogrIaItphy using a 15 Reoplex column, F and M Temperature ProgrammedDocosene-l (boiling point range of 687-705 F.) was employed on thedisplacing high molecular weight alpha olefin. The initial displacementwas carried out in an Asco 50-2 rota-film molecular still primarilybecause of the short residence time obtainable by this equip ment. Themole ratio of docosene-l to aluminum trialkyl was 4.5/1, the reactortemperature was 316 C. and the pressure was atmospheric (positive flowof N The aluminum trialkyl growth feed was fed through the still atthese conditions and the bottoms obtained was recycled through the stillat the same conditions. No apparent degradation of the bottoms productwas observed and this apparently is attributable to the docosene-lacting as a liquid carrier for the aluminum trialkyl.

The over-all conversion after both cycles was 77% based on C olefinconsumption to aluminum alkyl. The mole percent conversion for eachaluminum alkyl to pro- Q 7 ca duce the alpha olefin is shown in thefollowing tabula- Table IV tion:

Table II Mole Percent Conversion of AIR to a-Olefins Mole percentConversion of AlRa to n-alpha-olefin Run Number 1 2 3 4 Components 1stCycle 2d Cycle Average Temp., 0. 145 168 182 195 Aluminum Alkyls:

A1(C8H17)3 -100 -100 -100 A1 (041103 90.0 AMOwHmS 63.2 97.8 -100 -100.A1(O6 l3)3--- 61.0 87.8 A](C12['I25)3-- 56.8 93.5 -100 95.4 A a i1)3--39. 3 75.8 AMOHHM" 36.8 57. 0 68.7 72. 4 A1 (01011205-- 40. 8 72. 4.A.1(C1BII33)3- 33. 2 17. 4 27. 1 42. 3 'Al (o 2H25)3 41. 3 69. 8 Al(C1Ha1)3 10. 0 25. 5 A1 (014mm- 37. 0 60. 5 Al (C1tH33)3- 22. 1 50. 5 Al(Ci H 1);- 16. 6 20.0 15 1 At residence tune of about two hours.

The highest over-all conversion was obtained from Run 4 From this run,it is apparent that conversions can be obin which a conversion of 76.1%of Al(C1 H37)3 and lighttained reaching percent conversions of over 90percent er alkyl to their corresponding n-a-olcfin was found. In withoptimum conditions. The total aluminum loss was all the batchexperiments, the solution of alkyl and Ole 2.2 Wt. P r n i the unt oflighter aluminum fins remained clear and amber in colour during thecomalkyls vaporized and removed overhead along with the plete run. Thissuggests that the aluminum alkyls were displaced alpha olefins.remarkably thermally stable to decomposition at these EXAMPLE Hconditions since no visible precipitation of aluminum metal was noted.Additional runs employing docosene-l (herein a C EXAMPLE IV 0 C alphaolefin) were made. The 1n1t1al displacement was made in an Asco 50-2rota-film. The feed com In another displacement experiment octadecene-lpositions, feed rates, temperatures and test periods em- (b ili pointrange 596 5( 6 was used as the ployed are as set forth belowplacing highmolecular weight a-olefin. The run was carried out in a continuousvacuum fractionator where Run No. 2 the mole ratio of C olefin to AlRwas 2.6/1, the reactor Condltwns Run 1 temperature was 177 C., thepressure was 5 mm. of Hg 1st Pass 2d Pass and the average residence timecalculated was about thirty minutes. Under these conditions, an over-allcon- Feed, wt. percent: 1 version of 58% was obtained based on C olefincon- 3 55 33 3 55; E Sumption to aluminum alkyl. The mole percent con-Total charge, g 624.4 863.3 355.8 version of each aluminum alkyl toproduce n-alpha-olefin gf g fi f Mm 316 mm 1 is summarized in thefollowing tabulation: Feed Rate, cc./m 7.0 6.0 6.06 Test Period, min 12018 74 Mole Ratio of 0 0-024 a-olefin to 5. 0/1 6.1/1 3. 0/1 40 A1123.Mole Percent Conver- Components sion of AlR to n-alpha-olefin 1 Bottomfrom 1st cycle.

The experimental data are outlined in Table III. AMQHQ), 7&4 p .Al(C H81.5 Table Ill auogrriiii 81.0 Al(C10H 79. 2 Al(Ci2H2s)3 68. 2 Molepercent Conversion of AlR to n-alpha-olefm omponen S Run No. 2 EXAMPLE vRun N0. 1

1 tP SS 2d Pass An additional experiment was earned out using octa- S adecene-l displacement with the use of a continuous 1 H 94 4 95 6 99 4vacuum fractionator and is summarized in the following 2 tabulation. A2.5/1 mole ratio of octadecene-l to alu- Al 281252555- $2 g g 3-? minumtrialkyl was used and 70% of the displacing olefin Al (CiZHZZfiL--- 52:666:1 65:4 was converted to aluminum trioctadecyl. Infrared ana- A1(018E393 lysis indicate the displaced n-tx-olefins to be essentiallypure. The best results taken from Run No. 2, second pass, 60 show thatover 95% conversion of alkyls up to and 1ncluding Al(C H can beattained. The over-all con- Mole Percent Con- C t fAlR version of AlR upto Al(C H 1n Run No. 2, second Omponen s figif f g pass, uponcalculation is 87.7%.

Al Bu "8.4 EXAMPLE In mani {30,4 A1(OaH17)a 79.2 Batch type experimentswere carried out in a stirred (010E293 A1(C12 25)a 58. 1 reactor 1norder to determine the effect of temperature A1(C iH 9)3 23.0 exposuretime on docosene-l displacement products. Preliminary data for lowtemperature doc-osene-l displacement of growth alkyls are outlined inTable IV. The EXAMPLE VI reactor temperatures for the Runs 1 to 4 rangedfrom 140 to 200 C., respectively. The following is a sum- The followingexample represents a comparison of the marized tabulation comparing themole percent converdouble displacement with docosene-l and ethylene a dsion of each aluminum alkyl for each run: hexene and ethylene used inconjunction with a C average chain growth alkyl used as feed. In bothinstances the ethylene displacement was substantially identical. Inaccordance with the prior art practice one flash. and two fractionationsteps were added to the prior art process, thus, illustrating thesimplicity of the process of the present invention. 'The results aresummarized as follows:

EXAMPLE VII Additional runs were made in order to compare C olefindisplacement with C olefin displacement. The following is a tabulationcomparing the mole per cent conversion of each aluminum alkyl betweendocosene-l displacement and hexene-l displacement.

Percent Conversion of AlRa to n-a-Olefins Run No 1 2 3 4 Temp" C 300 300238 285 Pressure 1 20 2 50 2 50 Olefin/AlRa Mole Ba 4. 92 5. 87 54.1 52.6 Residence Time, Sec -20 -20 0.42 0.37 Over-all Conversion, Percent.-.74. 86. 3 74. 0 85.9 Components:

A1(C3H|7)3 93. 7 95. 2 85. 9 90. 7 Al(C|oH21)3 88.3 91. 4 88.0 90.1Al(C12H2s)a.. 78. 6 85. 6 78. 1 88. 3 Al(CnHza a- 71. 4 79. 71. 4 85. 7A1(CiuHsa)s 47. 7 75. 6 56. 8 77. 5 A1(C13H37)3 45. 2 64. 4 48. 5 71. 6

l Mm. Hg. 2 P.s.i.g.

When comparing docosene-l and hexene-l displacement conversions, itshould be noted that the C olefin displacing olefin yielded higherconversions for aluminum tridecyl and lighter alkyls.

From the foregoing data, it is obvious that the advantages of thepresent invention comprise at least:

(1) Lower recycle rates of C -C displacing olefin. (2) Aluminum triethylseparation simplified. (3) Elimination of fractionating equipment.

What is claimed is:

1. A process for the preparation of olefins which comprises reacting atrialkyl aluminum reactant having 2-3 carbon atoms per alkyl group withethylene under elevated temperatures and ethylene pressures whereby atrialkyl aluminum growth product having from about 2-2 4+ carbon atomsper alkyl group is obtained, reacting said growth product in a firstdisplacement stage with displacing olefins having at least 18 atoms andup to about 22 carbon atoms at temperatures of about ZOO-350 C.,pressures of about 0.1 mm. to 2 atmospheres and for periods of up to twohours, simultaneously and continuously removing the lower molecularweightolefins which are displaced by said displacing olefins and forminga first stage alkyl aluminum displacement product, reacting in a secondstage said first stage alkyl aluminum displacement product with a C -Colefin to obtain a mixture of first stage displacing olefins and asecond stage alkyl aluminum displacement product and distilling overheadfrom said mixture said second stage alkyl aluminum displacement product.

2. A process for the preparation of olefins which comprises reactingtriethyl aluminum with ethylene under elevated temperatures and ethylenepressures whereby an alkyl aluminum growth product having from about224+ carbon atoms per alkyl group is obtained, reacting said growthproduct in a first displacement stage with displacing olefins having aPoisson distribution of from 18+ to 22+ carbon atoms at temperatures ofabout 200- 350 C., pressures of about 0.1 mm. to 2 atmospheres and forperiods of up to two hours, simultaneously and continuously removing thelower molecular weight olefins which are displaced by said displacingolefins and forming a first stage alkyl aluminum displacement product,reacting in a second displacement stage said first stage alkyl aluminumdisplacement product with ethylene to produce a mixture of higherboiling first stage displacing olefins and triethyl aluminum, separatingsaid triethyl aluminum obtained in said second stage displacementreaction from the higher boiling olefins admixed therewith and employingsaid separated triethyl aluminum as initial growth reactant.

3. A process for the preparation of olefins which comprises reactingtriethyl aluminum with ethylene under elevated temperatures andpressures whereby a higher molecular weight trialkyl aluminum growthproduct is obtained, reacting said higher molecular weight trialkylaluminum growth product with docosene-l at temperatures of about ZOO-350C., pressures of about 0.1 mm. to 2 atmospheres and for periods of up totwo hours to form a mixture of docosyl aluminum and olefinscorresponding to the alkyl groups in said higher molecular weighttrialkyl aluminum growth products, simultaneously and continuouslyseparating from said displacement reaction product mixture olefinsboiling below the boiling point of tridocosyl aluminum, reacting theremaining tridocosyl aluminum and olefins boiling within the range of,and higher than the boiling point of tributyl aluminum with ethylene toform triethyl aluminum and olefins boiling substantially higher thantriethyl aluminum, separating said triethyl aluminum from said higherolefins and reacting said separated triethyl aluminum with additionalethylene.

4. A process in accordance with claim 3 wherein said growth reaction iscarried out at a temperature of 200- 500 F. and a pressure of '25500atmospheres for -a period of 0.5 minute to five hours.

5. In a process for producing olefins wherein triethyl aluminum isreacted with ethylene to form a trialkyl aluminum growth product and thealkyl groups of said trialkyl aluminum growth product are displacedtherefrom by reaction with displacing higher olefins, the improvementwhich comprises reacting said trialkyl aluminum growth product withdocosene-l in a first displacement reaction stage at temperatures ofabout 200350 C., pressures of about 0.1 mm. to 2 atmospheres and forperiods of up to two hours to form a mixture of tridocosyl aluminum andolefins corresponding to the alkyl groups in the trialkyl aluminumgrowth products, simultaneously and continuously separating C andlighter olefins from the tridocosyl aluminum formed in said firstdisplacement reaction and higher olefins, subsequently reacting themixed tridocosyl aluminum and C and higher olefins with ethylene to formtriethyl aluminum admixed with C and higher olefins and separating saidC and 3,278,633 11 12 higher olefins from the resultant triethylaluminum by OTHER REFERENCES distilhng said triethyl alurnlnum overPolymerization and Polycondensation Processes, Ad-

vances in Chemistry Series 34, A.C.S., Washington, DC.

References Cited by the Examiner 1962 pages 52 UNITED STATES PATENTS2,863,896 12/1958 Johnson 260683.15 DELBERT'E'GANTZPmmyEmmme" 2,889,3856/1959 Catterall et a1. 260683.15 R. H. SHUBERT, Assistant Examiner.

1. A PROCESS FOR THE PREPARATION OF OLEFINS WHICH COMPRISES REACTING ATRIALKYL ALUMINUM REACTANTS HAVING 2-3 CARBON ATOMS PER ALKYL GROUP WITHETHYLENE UNDER ELEVATED TEMPERATURES AND ETHYLENE PRESSURES WHEREBY ATRIALKL ALUMINUM GROWTH PRODUCT HAVING FROM ABOUT 2-24+CARBONS ATOMS PERALKYL GROUP IS OBTAINED, REACTING SAID GROWTH PRODUCT IN A FIRSTDISPLACEMENT STAGE WITH DISPLACING OLEFINS HAVING AT LEAST 18 ATOMS ANDUP TO ABOUT 22 CARBON ATOMS AT TEMPERATURES OF ABOUT 200-350*C.,PRESSURES OF ABOUT 0.1MM. TO 2 ATMOSPHERES AND FOR PERIODS OF UP 5O TWOHOURS, SIMULTANEOUSLY AND CONTINUOULSY REMOVING THE LOWER MOLECULARWEIGHT OLEFINS WHICH ARE DISPLACED BY SAID DISPLACING OLEFINS ANDFORMING A FIRST STAGE ALKYL ALUMINUM DISPLACEMENT PRODUCT, REACTING IN ASECOND STAGE SAID FIRST STAGE ALKYL ALUMINUM DISPLACEMENT STAGE PRODUCTWITH A C2-C3 OLEFIN TO OBTAIN A MIXTURE OF FIRST STAGE DISPLACINGOLEFINS AND A SECOND STAGE ALKYL ALUMINUM DISPLACEMENT PRODUCT ANDDISTILLING OVERHEAD FROM SAID MIXTURE SAID SECOND STAGE ALKYL ALUMINUMDISPLACEMENT PRODUCT.